Once Min accounted for other relevant factors, however, such as smoking, blood sugar, age and particulate pollution exposure there was a statistically significant increase in infertility for men who experienced noise above 55 decibels (similar to light traffic) at night. The association Min found was non-linear small increases in sound levels below the 55 dB threshold did not appear to have any effect on sperm production or quality, perhaps because people get used to noises up to a certain level. An association was also seen between infertility and exposure to slightly louder noises (60 dB) during the daytime, but this may reflect the fact that neighborhoods that are noisy at night are also likely to have more sound during the day.]